She always watches her son ________ the road every morning, or she will feel worried.
A. crossing B. cross C. to cross D. to crossing
Finally, people found computers ________.
A. useful B. are useful C. don’t useful D. doesn’t useful
They still can’t decide ________ with our difficulties in learning math.
A. what to deal B. how to do C. what to solve D. how to deal
Everybody tells us we can’t pass the exam ________ we study hard.
A. because B. or C. unless D. and
– How do you learn English, Tony?
– I usually practice English ________ chatting with my American friends.
A. in B. with C. on D. by
His father is engi
neer.
He designed such useful
machine
A．a an B. an a C. an an D. a a
